The present invention relates to a technique for forming optical devices and more particularly, to a technique for removing defects in a lens caused during the forming process.
In the prior art, a variety of techniques have been employed which facilitate the formation and manipulation of a lens during construction. Normally, a lens blank is first formed from conventional plastic material and worked or machined to form the finished lens product. In order to hold the lens during such machining, a holder must be employed to position and move the lens for appropriate modifications. In one such technique, the holder is formed as a low melting point alloy block (LMPA) which is applied to one surface of the lens and used to support the lens during machining. Afterwards, the block is removed from the lens surface and the lens used for forming eyeglasses and such.
While the above technique has been found to be simple and effective in operation, it has been discovered that a certain percentage of the lenses formed have defects in the lens surface following removal of the low melting point alloy block. The defects appear as warping, aberations or distortions and are believed to be caused by the heat from the application of the low melting point alloy to the surface of the lens. Such defects are not acceptable and therefore cause such lenses to be discarded as waste in the lens forming process.
Although the number of lenses exhibiting the presence of a defect in the formation process is only a relatively small percentage of the total number of lenses made, any reduction in the number of wasted lenses would decrease the cost per lens and increase the efficiency of the process. Accordingly, the present invention has been developed to overcome the shortcomings of the above known and similar techniques and to provide a process for eliminating defects caused during lens formation.